New method of vacuum deposition is reviewed for the control of phase-separated structure of crystalline donors and acceptors in organic photovoltaic cells. This method utilizes a liquid as a non-sticking co-evaporant of small molecular organic semiconductors and crystallizes their single and blend films. Blend films based on H₂Pc and C₆₀ with much improved crystallinity have been produced by this method and confirmed by analysis using UV-Vis, XRD and FESEM. Used in organic photovoltaic cells, a variety of blend films, such as blends of fullerenes (acceptors) and H₂Pc, PbPc, AlPcCl, and rubrene (donors), have been produced by this method and have achieved striking enhancement of short-circuit current density. In this manuscript, we also present the principle of this new method, co-evaporant induced crystallization. Since it drastically improve the principle of vacuum deposition of organic semiconductors, this method would not be limited for organic photovoltaic cells but be useful for other organic devices.